In a conventional packet of cigarettes, the group of cigarettes is wrapped internally in a rectangular sheet of foil inner packing material with no glue, and is packed externally in a rectangular sheet of outer packing material stabilized with glue.
Tobacco is highly sensitive to environment. That is, in contact with the atmosphere, its organic characteristics tend to vary alongside variations in humidity (by losing or absorbing too much moisture) or due to evaporation of the volatile substances with which the tobacco is impregnated (especially in the case of aromatic cigarettes treated with spices such as cloves). To preserve the tobacco, packets of cigarettes are therefore cellophane-wrapped, i.e. wrapped in a heat-sealed overwrapping of airtight plastic material. This, however, may not always be sufficient to fully preserve the organic characteristics of the tobacco in the packet, especially if the packet is consumed some time after manufacture. Moreover, when the packet is unsealed, the overwrapping is removed, thus exposing the tobacco to the atmosphere, and, if the cigarettes are not consumed soon after the packet is unsealed, the organic characteristics of the remaining cigarettes may deteriorate visibly.
In an attempt to eliminate this drawback, rigid packets of cigarettes have been proposed, in which the inner package is airtight, and comprises a sheet of airtight, heat-seal packing material having a cigarette extraction opening closed by a reusable cover flap. In other words, the cover flap has fastening means (e.g. a strip of non-dry re-stick adhesive) by which to repeatedly secure the cover flap in a closed position closing the cigarette extraction opening.
It has been observed that folding the sheet of inner packing material about the group of cigarettes may damage the tips of the cigarettes (i.e. the plain ends opposite the filter, where the tobacco is exposed), thus resulting in localized deformation and/or tobacco spill (i.e. tobacco fallout from the tips). This applies in particular to the corner cigarettes in the group, though damage is also evident in all the outermost cigarettes, i.e. located along the fold lines of the sheet of inner packing material. Folding a sheet of airtight inner packing material subjects the cigarettes to even more damage, by being thicker (and therefore stiffer) than conventional sheets of foil inner packing material. Moreover, at the cover flap (where the first end fold is made), the sheet of airtight inner packing material is even thicker and therefore locally extremely stiff.
To avoid damaging the cigarettes when folding a sheet of airtight inner packing material, it has been proposed to fold the sheet of airtight inner packing material first about a folding spindle to form a tubular wrapping with an open end; insert the group of cigarettes into the tubular wrapping through the open end; and complete folding of the sheet of airtight inner packing material by closing the open end onto the group of cigarettes. The method currently used to fold a sheet of airtight inner packing material, however, has the drawback of forming two longitudinal steps inside the tubular wrapping, at the closed end opposite the open end, and which impede insertion of the group of cigarettes into the tubular wrapping through the open end. In other words, as it slides inside the tubular wrapping, the group of cigarettes may strike and deform the steps, and so longitudinally reduce the space in which to accommodate the cigarettes. As a result, when inserting the group of cigarettes inside the tubular wrapping and closing the open end, the cigarettes are compressed longitudinally and therefore inevitably damaged.
Examples of folding a sheet of inner packing material about a group of cigarettes are described in Patent GB78507GA and Patent Application IT2006BO00347.
An airtight inner package made from a sheet of airtight, heat-seal packing material may sometimes “balloon” on account of surplus air trapped inside when forming the inner package. This “balloon” look is particularly undesirable, by being unsightly, and by increasing the size of the inner package and so making it difficult to fold the outer package around it.